Substance mixture containing bisphenol a

ABSTRACT

The invention relates to substance mixtures, containing bisphenol A, two methods for production thereof and use thereof for production of polymeric materials.

[0001] The present invention relates to mixtures of substancescontaining bisphenol A as well as two processes for the preparationthereof and their use for preparing polymer materials.

[0002] Bis(4-hydroxyaryl)alkanes, in the following called bisphenols,are important as starting materials or as intermediates for preparing anumber of commercial products. Bisphenols can be prepared by thecondensation of phenols and carbonyl compounds. Substituted phenols orunsubstituted phenol may be used.

[0003] The condensation product from the reaction between phenol andacetone, 2,2-bis(4 hydroxyphenyl)propane (bisphenol A, BPA, p,p-BPA) isof particular industrial importance. BPA is used as a starting materialfor preparing various types of polymer materials such as, for example,polyarylates, polyetherimides, polysulfones and modifiedphenol/formaldehyde resins. Preferred areas of application are thepreparation of epoxy resins and polycarbonates.

[0004] Processes for preparing bisphenols by acid-catalysed reaction ofphenols with carbonyl compounds are known, for example from U.S. Pat.No. 2,775,620 and from EP-A-0 342 758.

[0005] Bisphenols of general structure can be prepared by processeswhich are analogous to the preparation of BPA.

[0006] Phenol resins are artificial resins which are obtained by thecondensation of phenols (or bisphenol A) with aldehydes, in particularformaldehyde, by derivatisation of the condensates resulting therefromor by the addition of phenols to unsaturated compounds such as e.g.acetylene, terpenes or natural resins.

[0007] Compounds called epoxide resins are either oligomeric compoundswith more than one epoxide group per mole, which are used to preparethermoset materials, or else the corresponding thermoset materialsthemselves. The conversion of epoxide resins is achieved viapolyaddition reactions with suitable hardeners or by polymerisation viathe epoxide group. More than 90% of current world-wide production takesplace by reacting bisphenol A with epichlorhydrin.

[0008] The term formaldehyde resins includes the industrially veryimportant urea, melamine, phenol and, in a wider sense, furan resinswhich are prepared by condensation of formaldehyde with urea, melamine,phenol or phenols (including bisphenol A) and furfuryl alcohol asmonomers which contain NH or OH groups.

[0009] Polymer materials such as, for example, phenol resins, epoxideresins or formaldehyde resins may be prepared using bisphenol A as a rawmaterial. The disadvantage of this is that bisphenol A in the pure formis expensive, and in addition it is disadvantageous that the propertiesof the polymer materials mentioned are not optimal when they areprepared using pure bisphenol A as a raw material.

[0010] Thus, the present invention is based on the object of providing aprocess for preparing polymer materials, for example phenol resins,epoxide resins or formaldehyde resins, which does not have thedisadvantages of the prior art mentioned above.

[0011] The object according to the invention is the use of a mixture ofsubstances containing bisphenol A and secondary products which areproduced during the production of bisphenol A to prepare polymermaterials such as, for example, phenol resins, epoxide resins orformaldehyde resins.

[0012] The present invention therefore provides a mixture of substancescontaining bisphenol A and secondary products which are produced duringthe production of bisphenol A.

[0013] The mixture of substances according to the invention contains(data in wt. %):

[0014] p,p-BPA: 35 to 75, preferably 40 to 65

[0015] o,p-BPA: 5 to 25, preferably 10 to 20

[0016] sum of bisphenols (p,p-BPA+o,o-BPA): 50 to 80, preferably 60 to70

[0017] secondary products which are produced during the production ofbisphenol A: 50 to 20, preferably 40 to 30.

[0018] The sum of the proportions by weight of p,p-BPA and o,p-BPA andthe secondary products is 100 wt. %.

[0019] Secondary products which are produced during the production ofbisphenol A are, according to the invention, isomers ofpara,para-bisphenol A, chromanes, indanes, phenols, higher condensatesof the substances mentioned, and also other compounds the structure ofwhich is not explained in detail.

[0020] The mixture of substances according to the invention may alsocontain between 0 and 90 wt. %, preferably 0 to 60 wt. %, veryparticularly preferably 0 to 50 wt. % of phenol, with respect to thetotal weight of the mixture being produced therewith.

[0021] A composition differing from the composition according to theinvention is a disadvantage when preparing e.g. phenol resins. If, forexample, the proportion of the highly reactive component phenol isincreased to more than 60 wt. %, then the rate of reaction in the commonprocesses for preparing e.g. sheets based on thermosetting resins is toohigh. The mixture according to the invention exhibits advantages, ascompared with pure phenol, in controlling the rate of reaction and thestructure of the polymer by targeted introduction of cross-linking andbranching sites.

[0022] The present invention also provides use of the mixtures ofsubstances mentioned for preparing polymer materials, for example phenolresins, epoxide resins or formaldehyde resins.

[0023] The present invention also provides three different processes forpreparing the mixtures of substances according to the invention, whichare described in the following three paragraphs:

[0024] A process for preparing the mixture of substances according tothe invention, wherein in the process for preparing bisphenol A, asubstream is taken from the mother liquor produced duringcrystallisation and filtration, after dewatering, and this is preferablyrendered inert, preferably after separation of any phenol which is stillpresent, and then put into containers.

[0025] A process for preparing the mixture of substances according tothe invention, wherein in the process for preparing bisphenol A, asubstream is taken from the mother liquor obtained duringcrystallisation and filtration, after dewatering, and this is suppliedto a rearrangement reaction at temperatures between 50° C. and 90° C.with residence times of 2 to 12 hours on an acid ion-exchanger (some ofthe secondary products are then rearranged to give p,p-bisphenol A) anda substream is taken from this rearranged product which is renderedinert, preferably after separation of any phenol still present, and thenput into containers.

[0026] A process for preparing a mixture of substances according to theinvention, wherein in the process for preparing bisphenol A, a substreamis taken from the mother liquor obtained during crystallisation andfiltration, after dewatering, and this is then preferably supplied to arearrangement reaction at temperatures between 50 and 90° C. withresidence times of 2 to 12 hours on an acid ion-exchanger (some of thesecondary products are then rearranged to give p,p′-bisphenol A) and isthen concentrated by distillation, a crystalline bisphenol A phenoladduct is then extracted from this by crystallisation at a temperatureof 40 to 50° C. with a residence time of 1 to 6 hours and isolated byfiltration and the remaining liquid mixture, preferably after separationof any phenol still present, is rendered inert and then put intocontainers.

[0027] The present invention has many advantages; in particular,mixtures of substances according to the invention are of high qualityand have good storage stability. They are used as raw materials forpreparing high quality polymer materials such as, for example, phenolresins, epoxide resins or formaldehyde resins.

[0028] Mixtures of substances according to the invention are preferablydiluted with phenol, when the phenol used is preferably acid-free,alkali-free and metal-free.

[0029] Mixtures of substances according to the invention are preferablyprepared under inert conditions, i.e. in particular with the exclusionof oxygen.

[0030] Mixtures of substances according to the invention haveadvantages, as compared with pure bisphenol A, as raw materials for thepreparation of the polymer materials mentioned. For example, regulatingthe rate of polymerisation is simpler and in addition targetedcross-linking and branching sites are introduced to the polymermaterials mentioned by the mixtures of substances according to theinvention.

[0031] A composition for the mixture of substances which differs fromthe composition according to the invention is disadvantageous for thepreparation of polymer materials such as, for example, phenol resins.If, for example, the proportion of the highly reactive component phenolis increased to more than 60 wt. %, in particular more than 90 wt. %,then the rate of reaction is too high in common processes for preparingproducts, for example sheets based on thermosetting resins. Mixtures ofsubstances according to the invention exhibit, as compared with purephenol, advantages in regulating the rate of reaction and the structureof the polymer by targeted introduction of cross-linking and branchingpoints into the polymer material.

[0032] The process according to the invention for preparing BPA ispreferably based on the acid-catalysed reaction of phenol with acetone,wherein a ratio by amounts of phenol:acetone of greater than 5:1 is usedin the reaction. Homogeneous or heterogeneous Bronsted acids or Lewisacids are used as acid catalysts, that is, for example, strong mineralacids such as hydrochloric acid or sulfuric acid. Gel-like ormacroporous sulfonated cross-linked polystyrene resins (acid ionexchangers) are preferably used. The details given below refer to aprocess of preparation using acid ion exchangers as catalysts.

[0033] In order to produce high selectivity, the reaction of phenol withacetone can be performed in the presence of suitable mercapto compoundsas cocatalysts. These may either be dissolved homogeneously in thereaction solution or be fixed to the sulfonated polystyrene matrix viaionic or covalent bonds. The reaction unit is preferably a fixed layerbed or a fluidised bed which is traversed upwards or downwards or acolumn of the reactive distillation column type.

[0034] During the reaction of phenol with acetone in the presence ofacid catalysts and mercapto compounds as cocatalysts, a product mixtureis produced which contains, in addition to unreacted phenol andoptionally acetone, primarily BPA and water. In addition, there are alsosmall amounts of typical secondary products of the condensation reactionsuch as, for example, 2-(4-hydroxyphenyl)-2-(2-hydroxyphenyl)propane(o,p-BPA), substituted indenes, hydroxyphenyl indanoles, hydroxyphenylchromanes, substituted xanthenes and higher condensed compounds withthree or more phenyl rings in the molecular structure.

[0035] The secondary products mentioned, as well as water, phenol andacetone, may impair the suitability of BPA for preparing polymers andhave to be separated by suitable methods. High specifications relatingto purity are generally required for the raw material BPA, in particularwhen preparing polycarbonate.

[0036] The working up and purification of BPA is normally performed bymeans of a multistage cascade of suitable purification processes suchas, for example, suspension crystallisation, melt crystallisation,distillation and desorption. In an industrially preferred embodiment,BPA is isolated from the reaction mixture in the form of anapproximately equimolar crystalline adduct with phenol by cooling thereaction mixture, when the BPA/phenol adduct crystallises out. Thecrystallisation process is preferably performed as a suspensioncrystallisation. Suspension crystallisation is understood to becrystallisation from a liquid due to cooling, wherein the crystals forma suspension with the liquid (solid/liquid). The BPA/phenol adductcrystals are then separated from the liquid phase, using equipmentsuitable for solid/liquid separation such as a rotary filter or acentrifuge, and if required taken on for further purification. Thus,adduct crystals are obtained which typically have a purity greater than99 wt. % of BPA, with respect to the secondary components, with a phenolcontent of about 40 wt. %. Impurities which adhere to the surface of theadduct crystals can be removed by washing with suitable solutions whichtypically contain one or more components from the group acetone, water,phenol, BPA and secondary components.

[0037] The stream of liquid (mother liquor) produced during solid/liquidseparation contains phenol, BPA, water produced during reaction andunreacted acetone and is enriched in the secondary components typicallyproduced during BPA preparation. In a preferred embodiment, this motherliquor is recycled to the reaction unit. In order to maintain thecatalytic activity of the acid ion exchanger any water produced ispreferably removed by distillation, wherein any acetone still present isalso optionally removed from the mother liquor. The dewatered reactionstream obtained in this way is topped up with phenol and acetone andreturned to the reaction unit. Alternatively, water and acetone may alsobe partly or entirely removed by distillation prior to performingsuspension crystallisation of the BPA/phenol adduct. During thedistillation steps described above, some of the phenol present in thereaction solution may also be removed by distillation.

[0038] In the case of this type of circulation procedure the problem isthat secondary products from the preparation of BPA accumulate in thecirculation stream and can lead to deactivation of the catalyst system.In order to avoid excessive accumulation of secondary components in thecirculation stream, some of the circulation stream, optionally afterpartial or complete recovery of phenol by distillation, is excluded fromthe process chain as a BPA resin.

[0039] In addition, it has proven advantageous to pass some or theentire amount of the circulation stream, after solid/liquid separationand before or after the removal of water and residual acetone, over arearrangement unit filled with acid ion exchanger. This unit isgenerally operated at a higher temperature than the reaction unit. Inthis rearrangement unit, under the conditions present therein, some ofthe secondary components from BPA preparation and present in thecirculation stream are isomerised to give BPA, so that the overall yieldof BPA can be increased.

[0040] The BPA/phenol adduct crystals obtained after the completion ofsuspension crystallisation of the reaction solution and solid/liquidseparation as described above are then taken, if required, to furtherpurification stages, wherein the isolation of phenol and optionally areduction in the concentration of secondary components is achieved.

[0041] Thus, the adduct crystals can be recrystallised, for example,from phenol, from organic solvents, from water or from mixtures of thecompounds mentioned in accordance with a suspension crystallisationprocedure. The phenol present in the adduct crystals can also beentirely or partly removed by choosing a suitable solvent. The phenoloptionally remaining in the BPA after recrystallisation can then beentirely removed by suitable distillation, desorption or extractionprocedures.

[0042] Alternatively, phenol can also be removed first from the adductcrystals. Preferred methods for this are desorption of the melt usinghot inert gases, vacuum distillation or a combination of the methodsmentioned. In this way, it is possible to obtain BPA with a residualphenol concentration of less than 100 ppm from the adduct crystals. Bymeans of suitable reaction management and optionally the addition ofstabilisers, it can be ensured that BPA does not decompose to a markedextent under the thermal stresses experienced during the removal ofphenol by distillation or desorption.

[0043] Depending on the process conditions for suspensioncrystallisation from the reaction solution and when performing thesolid/liquid separation and crystal washing, the BPA obtained issuitable for preparing polymer materials after the removal of phenolfrom the adduct crystals. It may be necessary to take the BPA obtainedafter the removal of phenol to a further purification operation, inparticular in order to prepare high quality materials such aspolycarbonates. Final purification may be performed by suspensioncrystallisation from water or suitable organic solvents, meltcrystallisation in the form of a static or dynamic layercrystallisation, extraction with water, aqueous neutral, acid or basicsalt solutions or suitable organic solvents or in the form of asingle-stage or multi-stage distillation. It is possible to obtain BPAwith a purity of greater than 99.9 wt. % by performing the purificationoperations mentioned, or a suitable combination thereof, this BPA beingespecially suitable for preparing high quality polymer materials.

[0044] A preferred embodiment of the present invention is characterisedin that, after dewatering, a substream is taken from the mother liquorproduced during crystallisation and filtration in the process describedfor preparing bisphenol A. This substream preferably corresponds to 5 to15 wt. % of the mother liquor produced. This substream preferablycontains less than 0.5 wt. % of water and preferably less than 0.1 wt. %of acetone. To prepare the mixture of substances according to theinvention, the substream mentioned above is preferably filtered, tracesof acid are preferably completely removed therefrom, then in any casethe mixture is rendered inert and put, at temperatures of preferably 60to 100° C., into containers which are preferably made of stainlesssteel.

[0045] Another preferred embodiment of the present invention ischaracterised in that a substream produced by the process according tothe preceding paragraph is isomerised at temperatures of preferably 50to 70° C., in particular 60 to 70° C., particularly preferably 65° C.,on an acid ion exchanger. Isomerisable constituents, for exampleo,p-bisphenol A, are thus isomerised to p,p-bisphenol A. The residencetime in the isomerisation reactor is preferably 2 to 12 hours, inparticular 3 to 8 hours, particularly preferably 3 to 4 hours. Toprepare the mixture of substances according to the invention, thesubstream is filtered after isomerisation, traces of acid are preferablycompletely removed therefrom, then in any case the mixture is renderedinert and put, at temperatures of preferably 60 to 100° C., intocontainers which are preferably made of stainless steel.

[0046] Another preferred embodiment of the present invention ischaracterised in that, after dewatering, a substream is taken from themother liquor produced during crystallisation and filtration in theprocess described for preparing bisphenol A. This substream preferablycorresponds to 5 to 15% of the mother liquor produced. This substreampreferably contains less than 0.5 wt. % of water and less than 0.1 wt. %of acetone. The substream is then converted in a rearrangement reactionat temperatures between 50 and 90° C. with residence times of 2 to 12hours, on an acid ion exchanger. The substream is then concentrated bydistillation. In this procedure phenol is substantially removed. Thephenol content after concentration is preferably less than 70 wt. %, inparticular less than 60 wt. %. The mixture concentrated in this way iscrystallised in a preferably 1-2 stage crystallisation at a temperatureof 40 to 50° C. with a residence time of 1 to 6 hours. The crystallisedbisphenol A/phenol adduct obtained in this way is isolated by filtrationand taken to the main process for preparation of bisphenol A. Theremaining liquid mixture, or a part thereof, optionally after furtherconcentration, wherein more phenol is removed, is preferably filtered inorder to prepare the mixture of substances according to the invention,traces of acid are preferably completely removed therefrom, then in anycase the mixture is rendered inert and put, at temperatures ofpreferably 80 to 125° C., into containers which are preferably made ofstainless steel.

[0047] Mixtures of substances according to the invention preferablycontain additional phenol in a proportion of 0 to 90 wt. %, inparticular 0 to 60 wt. %, particularly preferably 0 to 50 wt. %.

[0048] Drawing 1 shows, schematically, a process for preparing mixturesof substances according to the invention. The drawing represents apreferred embodiment of the invention; the scope of the invention is notrestricted to the drawing.

[0049] Phenol and acetone are supplied to unit 1 and react in unit 1 togive bisphenol A.

[0050] Crystallisation of the adduct of bisphenol A and phenol takesplace in unit 2. In addition, separation of the crystallised adducttakes place in unit 2. The separated adduct is taken to unit 3 in whichseparation and working up of the bisphenol A takes place. The remainingmother liquor is transferred from unit 2 into unit 4 in which theremoval of water (dewatering) takes place. A proportion of 85 to 95 wt.% is returned to unit 1 from unit 4, along with the supply of 2 to 6 wt.% of acetone. A mixture of substances according to the invention can beisolated after unit 4. The smaller part (5 to 15 wt. %) of the dewateredmother liquor in unit 4 is taken to unit 5. Rearrangement takes place inunit 5. A mixture of substances according to the invention can beisolated after unit 5. The rearranged mother liquor in unit 5 is takento unit 6. In unit 6, the removal of phenol and the crystallisation andisolation of bisphenol A/phenol adducts as solid take place byfiltration. A mixture of substances according to the invention can beisolated after unit 6 from the remaining mother liquor, optionally afterremoving any phenol still present by known processes such as e.g.distillation, desorption, etc. The recovered phenol is taken from unit 6to unit 1, along with the supply of 2 to 6 wt. % of acetone. Themixtures of substances according to the invention which are isolatedafter unit 4, 5 or 6, are supplied to a container filling procedure.

[0051] In the following, the invention is explained by means of exampleswithout restricting the scope of the invention to the examples.

[0052] In the following, mixtures of substances according to theinvention and their preparation are given by way of example. Preparationtakes place each time in an arrangement as described in FIG. 1.

[0053] The compositions cited for the mixtures of substances accordingto the invention refer to several batches which were prepared from eachmixture of substances. In each individual batch, the sum of all thecomponents was 100 wt. %.

[0054] A mixture of substances according to the invention (BPG 1) wasisolated after unit 4.

[0055] A mixture of substances according to the invention (BPG 2) wasisolated after unit 5.

[0056] A mixture of substances according to the invention (BPG 3) wasisolated after unit 6. BPG1 p,p-BPA 50 to 60 wt. % o,p-BPA 10 to 20 wt.% sum of bisphenols¹⁾ 65 to 75 wt. % trisphenols  0 to 5 wt. % indanes 0 to 10 wt. % chromanes  5 to 15 wt. % residual components²⁾ 30 to 2wt. % BPG2 p,p-BPA 60 to 70 wt. % o,p-BPA  5 to 15 wt. % sum ofbisphenols¹⁾ 65 to 75 wt. % trisphenols  0 to 3 wt. % indanes  0 to 10wt. % chromanes  5 to 15 wt. % residual components²⁾ 30 to 2 wt. % BPG3p,p-BPA 35 to 45 wt. % o,p-BPA 10 to 20 wt. % sum of bisphenols¹⁾ 55 to65 wt. % trisphenols  0 to 5 wt. % indanes  5 to 15 wt. % chromanes 15to 25 wt. % residual components²⁾ 30 to 2 wt. %

[0057] In the following, comparison examples are provided:

[0058] BPG4 was obtained in the same way as BPG1, but without removingacid or traces of acid. The water content of BPG4 was greater than 0.5wt. %. After a period of more than 5 days, BPG4 which initially had aconcentration of p,p-BPA of 50.2 wt. % and a concentration of residualcomponents of 29.4 wt. %, had decomposed. After decomposition, thecomposition of BPG4 was 47.7 wt. % of p,p-BPA and 32.2 wt. % of residualcomponents.

[0059] BPG5 was obtained in the same way as BPG2; the initial mixturefor rearrangement was a mixture of 50.2 wt. % of p,p-BPA and 8.2 wt. %of indanes. Rearrangement was performed under unsuitable conditions at80° C. and for 15 hours. The result was increased formation of indaneand decomposition of the p,p-BPA. After rearrangement under unsuitableconditions, BPG5 had a concentration of p,p-BPA of 42.7% and an indanecontent of 15.0 wt. %.

[0060] BPG6 was obtained in the same way as BPG3, but inertisingconditions were not applied. After a period of more than 5 days underambient conditions, a clear deterioration in colour, expressed as theiodine colour index, was produced. The iodine colour index increasedfrom 300 to more than 1,000. In addition, the concentration of p,p-BPAdecreased due to decomposition.

1. A mixture of substances containing 35 to 75 wt. % of p,p-bisphenol Aand 5 to 25 wt. % of o,p-bisphenol A and 20 to 50 wt. % of secondaryproducts which are produced during the preparation of bisphenol A,wherein the sum of the proportions by weight of p,p-bisphenol A ando,p-bisphenol A is 50 to 80 wt. % and wherein the sum of the proportionsby weight of p,p-bisphenol A and o,p-bisphenol A and the secondaryproducts is 100 wt. %.
 2. A mixture of substances according to claim 1,wherein the secondary products are isomers of p,p-BPA, chromanes,indanes, phenols, higher condensates of the substances mentioned, andother compounds the structure of which is not given in detail.
 3. Amixture of substances according to one of claims 1 or 2, which alsocontains 0 to 90 wt. % of phenol, with respect to the total weight ofthe mixture then produced.
 4. Use of the mixture of substances accordingto one of claims 1 to 3 to prepare polymer materials.
 5. Use of themixture of substances according to one of claims 1 to 3 to preparephenol resins, epoxide resins or formaldehyde resins.
 6. A process forpreparing the mixture of substances according to one of claims 1 to 3,wherein in the process for preparing bisphenol A a substream is takenfrom the mother liquor produced during crystallisation and filtration,after dewatering, and this is rendered inert and then put intocontainers.
 7. A process for preparing the mixture of substancesaccording to one of claims 1 to 3, wherein in the process for preparingbisphenol A a substream is taken from the mother liquor produced duringcrystallisation and filtration, after dewatering, this is thenconcentrated by distillation, a crystallised bisphenol A phenol adductis extracted from this by crystallisation at a temperature of 40 to 50°C. with a residence time of 1 to 6 hours and is isolated by filtrationand the remaining liquid mixture is rendered inert and then put intocontainers.